<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<title>三列布局的学习</title>
	<link rel="stylesheet" type="text/css" href="css/three.css">
</head>
<body>
	<header>我是header</header>
	<section id="content">
		<section class="primary">
			<div id="primary_main">我是主内容</div>
			<div id="primary_sub">我是次要内容</div>
		</section>
		<aside class="secondary">secondarysecondarysecondarysecondarysecondarysecondarysecondarysecondarysecondarysecondarysecondarysecondarysecondarysecondarysecondarysecondarysecondarysecondarysecondarysecondarysecondarysecondary</aside>
	</section>
	<footer>我是footer</footer>

</body>
</html>